Tunable Floquet topological magnons in a driven system

Topological magnon insulators are two-dimensional systems with an ordered magnetic ground state and gapped bosonic magnetic excitations (magnons). In the presence of an out-of-plane Dzyaloshinskii-Moriya interaction (DMI), a two-dimensional magnetic system may support excitations corresponding to bands of one-magnon and two-magnon modes. These bands may be topologically non-trivial (characterized by non-zero Chern numbers) and therefore these systems support chiral magnon edge states. Recently, Ref. [1] studied magnetic systems where the (otherwise trivial) single-magnon and two-magnon bands are hybridized by in-plane DMI, resulting in a topologically non-trivial band structure. We aim to find magnetic systems in which such hybridization between (initially trivial) bands having a different magnon number is achieved by driving the system with time-dependent electromagnetic fields. The resulting bands may have non-zero Chern numbers that can be modified by varying the relative phase between ac magnetic fields driven at two distinct frequencies. Furthermore, we study the transverse thermal conductivity in this system and investigate its deviation from the case of static (topologically trivial) systems.

[1] Mook, Alexander, et al. Phys. Rev. B 107.6 064429 (2023).